In present day microelectronics design, one ongoing goal is to reduce the size of any integrated circuit and to fit as much functionality as possible onto a single substrate. However, due to high power signals leakage and interferers (high power local oscillation signals leak through PCB substrate to interfere transmitter/receiver part) it is sometimes necessary to separate circuits onto different substrates and sometimes it's physically impossible to fit all components onto a single circuit board, thus making it necessary to place components on different circuit boards. It is therefore important to be able to interconnect the circuits between two circuit boards or substrates whilst maintaining a high performance and avoid limiting the available bandwidth.
One common way to interconnect circuit boards or substrates is to use bond wires or even bond strips, typically gold bond wires or strips. However, a bond wire or strip adds a low pass element to the microwave system and limits the bandwidth of the circuit. Some variants of interconnecting boards whilst enhancing the bandwidth of the board to board connection include using multiple bond wires has been shown in [1-2]. Other variants include gold bond strips [3], and a compensated microstrip line [4].
However, as mentioned above, a bond wire adds a low pass element to the microwave system and limits the bandwidth of the circuit. Broadband interconnection using bond wires can be achieved by adopting multiple bond wires [1-2] and compensated microstrip lines [3-4].
Using multiple golden bond wires result in cost increasing and it is impossible to use more than 5 piece bond wires due to process limitation, so the bandwidth is still limited by the limited quantity of bond wires. In a corresponding manner, the use of golden bond strip is extremely high cost due to using volume golden material. And finally, it is impossible to etch compensated microstrip line thinner than 0.1 mm due to printed circuit board (PCB) fabrication process, which limits its application. So it cannot be used on interconnection where the compensated microstrip line thinner than 0.1 mm.
There is thus a need to provide board-to-board interconnections that enable maintaining a high bandwidth for e.g. microwave applications whilst avoiding the above-described problems.